The United Nations Law of the Sea Treaty, which has been in effect since 1994, gives nations sovereignty over the waters for 12 nautical miles (13.8 miles or 22.2 kilometers) off of their coastline. This means that if you sail out of a US port, you are still in the United States until you are more than 12 nautical miles offshore. Beyond that, you are in international waters… until you get within 12 nautical miles of the coastline of another country.
Fishermen in Southern California were recently surprised by a new Mexican law that requires all anglers fishing in Mexican waters to carry a passport. Since Mexico controls the waters for 12 miles off their coast, this particularly effects popular destinations for fishing charters out of San Diego. The Coronado Islands and the Rockpile, both popular fishing spots for day outings, both are within Mexican territorial waters.
